I. Technical Field
The present invention relates to an implant which is intended to be placed in a blood vessel, of the type comprising:                an endoprosthesis which has a longitudinal axis and which can be deployed spontaneously in a radial manner from a compressed configuration to a dilated configuration, the endoprosthesis delimiting an inner passage for blood flow and an outer peripheral surface;        at least one runner for radial support which co-operates with the endoprosthesis, the runner comprising a separation surface which extends radially with respect to the outer surface and at least one member which can be deployed away from the longitudinal axis relative to the separation surface.        
The invention is used in particular for the replacement of a natural cardiac valve with an endovalve.
II. Description of the Prior Art
The heart comprises valves which are present at the outlet of the right ventricle (pulmonary valve) and the left ventricle (aortic valve).
These valves provide one-way circulation of the blood flow, preventing blood reflux following the ventricular contraction.
However, illnesses can affect the valves. In particular, the valves may be subject to calcification,. which thus allows reflux or regurgitation towards the ventricle which has discharged the blood flow. The problem of regurgitation leads to abnormal dilation of the ventricle which results in cardiac insufficiency in the long term.
In order to treat this type of illness in a surgical manner, the defective valve is replaced. In this manner, it is known to implant an endovalve between the leaflets which delimit the defective valve. This endovalve is constituted by a tubular endoprosthesis which is formed by a self-expandable trellis and a flexible shutter which is produced from tissue of animal origin. The flexible shutter is permanently fixed in the endoprosthesis.
Endovalves of this type may be implanted via the endoluminal route, which considerably limits the risks associated with the implantation of the valve, in particular in terms of mortality.
In some cases, endovalves are not entirely satisfactory. After implantation of the endovalve, the leaflets of the damaged natural valve are pressed against the wall of the vessel by the outer surface of the endoprosthesis.
There is a significant risk of complications when the leaflets of the valve to be replaced extend in a region referred to as the coronary sinus, where the left and right coronary arteries open. If the coronary arteries open below the plane which extends through the free edge of the leaflets of the valve, and if the leaflets are highly calcified, the leaflets are capable of blocking the coronary arteries, which may bring about an extended infarctus, or even death of the patient.
In order to overcome this problem, it is known from FR-A-2 828 263 to provide openings in the wall of the endoprosthesis which supports the valve and to place these openings opposite the coronary arteries.
In order to ensure the axial and angular positioning of the endoprosthesis, the endoprosthesis is provided with indexing arms which engage the leaflets of the defective valve in order to abut the base of these leaflets.
After being placed in position, the endoprosthesis is deployed. The force for deploying each arm away from the endoprosthesis is significantly less than the deployment force of the endoprosthesis. The endoprosthesis therefore presses against the walls of the vessel, securing the arms and the leaflets of the valve against these walls.
A solution of this type is not entirely satisfactory when the coronary arteries open below the plane delimited by the free edge of the leaflets. In this case, the leaflets may block the coronary arteries when they are pressed against the wall of the coronary sinus when the endoprosthesis is deployed.